This invention relates to sensor systems for viewing scenes, and, more particularly, such a sensor system that achieves a high resolution over a large area, with no moving parts in the system.
As used herein, a sensor system is a device that converts an image into a signal which may be further analyzed. The sensor system typically includes a sensor device and an optical system that images a scene onto the sensor device. The visible or non-visible energy radiated from a scene is imaged onto the sensor by the optical system. The sensor converts the energy of the imaged scene into electrical signals. These signals are displayed, stored, or processed by a computer to analyze the content of the scene.
A television camera is one type of sensor system that converts visible light to an electrical signal. In other applications, lighter, smaller sensor systems, such as those employing a planar sensor array, are used. Such a planar array sensor has a large number of individual sensor elements that each receive energy and produce a responsive electrical output signal. The type of energy to which the sensor responds is determined by the detailed structure of the sensor element. Sensor elements are available for a wide range of visible light, infrared, and other wavelengths of energy. The sensor elements are provided in a large array, which in some current approaches is 256.times.256 elements in size, but may be larger or smaller. Thus, the planar sensor array may have tens of thousands of individual sensor elements. An optical system is typically provided to focus a scene onto the planar sensor array.
The resolution of a sensor system, including a planar sensor array coupled with an optical system, is measured by the angular size of an object that is subtended by a sensor element. The smaller the angle that may be resolved, the higher the resolution of the sensor. For any one sensor element, it is usually the case that the greater the resolution, the smaller the field of view of the sensor.
To increase the field of view of the sensor system without a loss of resolution, a sensor system may be constructed to view a small angular scene. The sensor array is mounted on a gimballed support driven by a controllable motor. The gimbal is driven to scan across a larger scene, so that the sensor array views only a small portion of the scene at any moment. A complete, high resolution image of the entire scene can be constructed by storing the images taken as the sensor array is scanned.
The gimballed sensor array approach is widely used. In some instances it may not be acceptable, because the gimbal and drive system are heavy, or because the mechanical system cannot withstand high acceleration environments. In other instances, the time required to complete a scanning of the scene is too long. There therefore exists a need for an improved approach to a high-resolution, large-scene sensor, which does not require any moving parts such as a gimbal and drive system. The present invention fulfills this need, and further provides related advantages.